Description
Mattermost Desktop App versions <=5.13.3 fail to attach listeners restricting navigation to external sites within the Mattermost app which allows a malicious server to expose preload script functionality to untrusted servers via having a user open an external link in their Mattermost server. Mattermost Advisory ID: MMSA-2026-00596
Problem types
CWE-829: Inclusion of Functionality from Untrusted Control Sphere
Product status
Any version
5.13.4.0
Credits
N/A
References
mattermost.com/security-updates (MMSA-2026-00596)